Naturalistic Fallacy

Inferring an "ought" from an "is", or more generally a prescriptive statement from a descriptive one. First described by DavidHume.

Women have traditionally cared for children, therefore it is fit and proper that women's role in our society should be to look after children.
Prisons the world over are full of people who committed crimes, therefore it is foolish to believe than man is inherently good.
Our ancestors gathered nuts, berries and roots, and scavenged meat, so that's what Nature intended for us to do.

(Bread moved to PostHocErgoPropterHoc)

Contrast with:

Illegal drugs are a lucrative trade for the mob, therefore drug distribution should be severely punished.
- Or legalized ;-)

Another example,

Wasting children's time in boring classes trains them to withstand business meetings, therefore the school system is good.

Naturalistic fallacy depends on assuming that the current state of affairs is good, proper or natural.

Then it should be defined that way, no? "The naturalistic fallacy is the act of inferring prescriptive conclusions from existing conditions which are believed to be natural, but are in fact artificial" or something like that?''

After all, there are many cases where it seems perfectly reasonable to infer "ought" from "is". "Human beings have a certain physical configuration (arms, legs, torso, buttocks, etc.) therefore we ought to design furniture to conform to this configuration." Is that not "ought" from "is"? -- MikeSmith

Not quite. You're implying "furniture ought to conform to the human configuration" from "furniture ought to be comfortable". "Human beings have a certain configuration" just lets you get from one to the other.

http://personal.bgsu.edu/~roberth/uncon.html contains a discussion of how most or all oughts derive from the Instrumental Principle; that we ought to take the means to our ends. It's actually a discussion about the relationship between oughts but it's great reading all the same.

My addition to the definition of the NaturalisticFallacy is just a clarification, it isn't substantive. -- RichardKulisz

Consider: All triangles built in the past have three side-components; therefore, to build a triangle, you ought to have three side-components.

... The NaturalisticFallacy does not seem to apply to projective concepts, like 'triangle' or 'sphere', or even prototype concepts like 'spherical'. You cannot build a triangle with four sides unless you throw one away. I think 'ought' from 'is' can, in fact, be derived: synthesis from definition, definition from analysis and social agreement, analysis over description, description from perception.

Where does the 'ought' come from? Methinks the social agreement on the definition. I ought to mean the same thing by 'triangle' as you do, so I cannot make triangles have four sides anymore than the omnipotent being can make a rock so large she cannot lift it without forsaking her omnipotence.

Argh. You're going to confuse philosophy students if you call this (is-implying-ought) the "naturalistic fallacy" - they call it the "metaphysical descriptivist fallacy". To further muddy the waters, it's not clear to many philosophers that it is a fallacy: that is, at least some purely descriptive statements imply prescriptive statements.

Consider that if what we're discussing really is a fallacy, then you can never get from purely descriptive statements (naturalistic or supernaturalistic) to prescriptive statements in a purely rational way. So you're committed to the view that a purely rational person would never know what to do unless directly provided with prescriptive statements. This doesn't usually square with our views of ourselves as rational people.

Your statement above seems to imply that descriptive premises are somehow more 'natural' than prescriptive premises. Can you make a case for this? If not, then there really is no problem... because prescriptive statements will be around a'plenty for rational, deontic logic.

What is rational, by the way. We can only describe what we see, not knowing what seeing is anyway. But we are experiencing presence of other entities that seem to have similar perceptions of our shared surroundings, thus we can get some consensus about reality. That is what most of us can see exists. Not very good foundation for logic of any kind.

(By the way, since I've heard this definition a lot, I'm guessing there's at least some large community that terms is-implying-ought the "naturalistic fallacy" - is it debate coaches?) -- GeorgePaci

then you can never get from purely descriptive statements (naturalistic or supernaturalistic) to prescriptive statements in a purely rational way.

And why ought you? You assume things should be arranged in some way but there should be nothing to stop you from reconsidering from a new perspective.

We do it by assuming the Instrumental Principle, which it is rational to assume (contrary to your claim otherwise). Of course, this might not be "purely" rational, whatever that might mean. As if rationality weren't problematic enough by itself!

Here's an example of a philosophy student who's quite certain it is a fallacy: http://personal.bgsu.edu/~roberth/isought.html. I'm not sure I buy his reasoning but it's interesting all the same. -- rk

He (Robert) effectively defines presupposes as meaning logically implies. Hence nothing is implied unless it's presupposed! He illustrates this trivial point using is and ought, but is actually saying nothing significant about is and ought. His page merits zero out of ten.

It's kind of sad what comes up as the first google hit for this phrase. What appears to be a rigorous classification of logical fallacies boldly claims the existence of a type of logical reasoning coined as "Retroductive", with the following form:

All men are mortal Socrates is mortal Therefore, Socrates is a man

Breathtaking. Following this logical reasoning:

All dogs are mortal Socrates is mortal Therefore, Socrates is a dog

One who can't recognize UndistributedMiddle has got some real chutzpah to be writing pages on logical reasoning. This hasn't any bearing on the Naturalistic Fallacy itself (that'd be AdHominem after all ;) but it certainly goes to warn about trusting the authority of random page authors.

The easiest way in the evolution game to derive a prescriptive statement from a descriptive one is to have an environment in which a goal of a reflective player to be more successful makes this player more successful. And this is probably the only environment that makes some players reflective, allowing prescriptive statements to be possible at all. -- NikitaBelenki

See LegalizeCannabis?, WarOnSomeDrugs?